A synthesis of iron deposits in the eastern Tianshan, NW China

Abstract

The northern Xinjiang region is one of the most significant iron metallogenic provinces in China. Iron deposits are found mainly within three regions: the Altay, western Tianshan, and eastern Tianshan orogenic belts. Previous studies have elaborated on the genesis of Fe deposits in the Altay orogenic belt and western Tianshan. However, the geological characteristics and mineralization history of iron deposits in the eastern Tianshan are still poorly understood. In this paper I describe the geological characteristics of iron deposits in the eastern Tianshan, and discuss their genetic types as well as metallogenic-tectonic settings. Iron deposits are preferentially distributed in central and southern parts of the eastern Tianshan. The known iron deposits in the eastern Tianshan show characteristics of magmatic Fe–Ti–V (e.g., Weiya and Niumaoquan), sedimentary-metamorphic type (e.g., Tianhu), and iron skarn (e.g., Hongyuntan). In addition to the abovementioned iron deposits, many iron deposits in the eastern Tianshan are hosted in submarine volcanic rocks with well-developed skarn mineral assemblages. Their geological characteristics and magnetite compositions suggest that they may belong to distal skarns.SIMS zircon U–Pb analyses suggest that the Fe–Ti oxide ores from Niumaoquan and Weiya deposits were formed at 307.7 ​± ​1.3 ​Ma and 242.7 ​± ​1.9 ​Ma, respectively. Combined with available isotopic age data, the timing of Fe mineralization in the eastern Tianshan can be divided into four broad intervals: Early Ordovician–Early Silurian (476–438 ​Ma), Carboniferous (335–303 ​Ma), Early Permian (295–282 ​Ma), and Triassic (ca. 243 Ma). Each of these episodes corresponds to a period of subduction, post-collision, and intraplate tectonics during the Paleozoic and Mesozoic time.